Flash floods are no longer confined to traditionally vulnerable regions, with changing climatic patterns now creating new risk zones across the Indian subcontinent, researchers at the Indian Institute of Technology Gandhinagar have warned.
In a study published in the journal 'npj Natural Hazards', scientists analysed four decades of meteorological and disaster data to create a comprehensive hotspot map of India. Their findings confirm a disturbing trend -- the rise of flash floods in previously unaffected basins, driven by increasingly intense and frequent extreme rainfall.
“Flash flood hotspots are mainly centred in the Himalayas, West Coast, and Central India, with geomorphological factors driving flash floods in the Himalayas and hydrological factors (flashiness) in the West Coast and Central India,” the researchers noted.
The study revealed that nearly three-fourths of flash floods across the country result from a combination of extreme precipitation and saturated ground, the latter caused by prolonged or recent rainfall. Only one-fourth of the events are triggered solely by extreme rain, the authors wrote.
“The combination of extreme precipitation and wet antecedent conditions triggers most (nearly 3/4th) flash floods while the remaining (nearly 1/4th) are solely driven by extreme precipitation,” they added.
Using temperature records from the India Meteorological Department (IMD) for 1981–2020 and data from the Emergency Events Database (EM-DAT), the team was able to isolate flash floods from other forms of flooding and examine their specific patterns and causes.
Also read: Himalayan Havoc: Nature’s fury or human greed?
The study highlights that flash floods are hyper-local and rapid, often giving communities less than six hours between the onset of rain and peak flooding. Most of the flooding is driven by precipitation falling over just 18 hours, the researchers observed.
A critical insight, according to the team, is that several basins currently considered less vulnerable are now showing signs of emerging risk. “Extreme rainfall is becoming more common and intense in several basins not prone to flash floods, highlighting that the warming climate can lead to newer flash flood hotspots in the future.”
The Indian Himalayas remain especially prone due to their steep terrain and fragile landforms. “The land surface features of the Indian Himalayas make the region particularly vulnerable to unusual and extreme weather events, such as cloudbursts, extreme precipitation, flash floods, and avalanches,” the study noted. Scientists attribute the rise in such events to human-induced climate change.
On Tuesday, the vulnerability was laid bare once again when a cloudburst in Uttarkashi district of Uttarakhand unleashed flash floods, claiming at least four lives and impacting half of the high-altitude villages in Dharali. Approximately 130 residents were evacuated, and rescue operations were underway, officials confirmed.
As monsoon dynamics continue to intensify under the influence of global warming, researchers stress the urgent need for early warning systems, updated flood modelling, and robust infrastructure in both established and emerging flash flood zones.
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